Orangutans learn to build complex tree nests by watching their mothers

As night falls in the rainforests, orangutans climb into the canopy to construct intricate tree nests, displaying remarkable ingenuity.

These comfy platforms are carefully engineered beds, providing warmth, comfort, protection from predators, and even reduce mosquito bites.

Scientists have long wondered how young orangutans learn to master such complex architecture. Recent findings reveal that they acquire this skill through close observation and practice, a process called observational social learning.

Orangutans build nests for survival

Nest-building is essential for survival. Unlike many behaviors in animals, this skill is neither entirely instinctive nor quickly learned.

Orangutans must manipulate branches, twigs, and leaves with strength and dexterity while making decisions about materials and structure.

Night nests, far more elaborate than day nests, can include linings, pillows, blankets, and even roofs.

To build such structures requires both technical know-how and material knowledge, making nest-building a cognitively demanding task.

Young orangutans begin showing interest in nests at just six months, playing with leaves and branches.

Practice of basic day nests starts around age one, but night nest practice begins only at three years and is not mastered until about the age of eight.

Complex additions, such as multitree nests and comfort elements, appear later. This long timeline shows that the skill is not acquired quickly but gradually, with repeated attempts and guided observation.

Learning from mom

Researchers documented that immatures who carefully peered at their mothers during nest-building were far more likely to practice soon afterward.

Merely being nearby without watching closely did not have the same effect. This highlights the importance of selective attention in learning.

“Nest-building is critical to survival in orangutans but is surprisingly not the focus of a lot of research,” noted Dr. Ani Permana from the University of Warwick.

“We previously reported that it takes multiple years for immature orangutans to learn to nest-build but, based on 17 years of observational data, this paper shows that this learning process is highly dependent on young animals carefully watching the nest-building of others.”

Orangutan nests are complex

The study also showed that young orangutans pay special attention to complex features like multitree nests, twig manipulations, and comfort elements.

These require memorizing multiple steps and sequences. After observing these, immatures increased their practice, suggesting they were specifically learning the more challenging parts.

Simpler nests, such as single-tree day nests, did not trigger the same level of focused observation.

“Orangutan nest-building tendency may have some innate basis, but the details and method must be socially learned, starting from a very young age, by watching and practicing, learning from mistakes as they grow and this paper is the first time this has been shown in wild apes,” Dr. Permana added.

At first, immatures mostly learn from their mothers, but as they grow older, they begin peering at other group members, thereby expanding their knowledge base.

Learning what to use

Beyond construction skills, orangutans also learn what materials to use.

“Aside from learning ‘how to’ build a nest, immature orangutans also appear to learn the ‘know-what’ of which materials to use,” noted Dr. Caroline Schuppli, Max Planck Institute of Animal Behavior.

The choice of tree species is important, and infants – who primarily peer at their mothers – are more likely to select the same species their mothers use.

“Just like human teenagers finding their own path, maturing orangutans increasingly peer at the nest-building of others and begin experimenting with the tree species those individuals use,” Dr. Schuppli continued.

Returning to roots

Interestingly, adults often revert to using the tree species favored by their mothers, even after experimenting with alternatives in youth.

“Ultimately, adult orangutans tend to revert to the nest materials used by their mothers, perhaps recognizing that the most effective methods had already been established,” Dr. Schuppli noted.

“This consistent variation in nest materials across generations indicates that wild orangutan populations possess cultural elements that could be lost without the conservation of the species and their habitats,”

Orangutans learn and pass on traditions

The study emphasized four main points: peering, not just proximity, drives learning; immatures focus on complex multi-step elements; role models expand with age; and knowledge of tree species is socially transmitted.

These findings suggest orangutans display cultural variation, with nest-building traditions passed through generations.

Nest-building is an evolutionarily ancient behavior shared by great apes.

By proving that orangutans acquire this skill through observational social learning, the study suggests that such cultural learning has deep roots in primate history.

It highlights not just the intelligence of orangutans but also their fragile cultural heritage – one that can only continue if their forest homes are preserved.

The study is published in the journal Communications Biology.

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